In recent years cosmetic compositions which improve the appearance of skin have become popular with consumers. There is at the present time a demand for cosmetic compositions which counteract or prevent the visible signs of aged and/or dry skin.
Skin cell proliferation is a process required for growth and repair, and it decreases with aging or photodamage. The synthesis of collagen (a predominant skin protein) also decreases with aging or photodamage. The present invention is based at least in part on the discovery that increased skin cell proliferation and collagen synthesis, which, in turn, is associated with improved condition and appearance of the skin, can be attained by incorporating a specific combination of a lactate dehydrogenase inhibitor with a carboxylic acid into topical treatment compositions.
Cutaneous tissues (skin cells, hair follicles, nails) obtain glucose (the source of bioenergy) predominantly from blood. Glucose is then enzymatically degraded to pyruvate. Pyruvate is subsequently metabolized within the cutaneous tissues via at least three routes. In the first route, pyruvate is oxidized to form the acetyl group of acetyl-coenzyme A, which is then oxidized completely to CO.sub.2 and H.sub.2 O via the Krebs cycle. In the second route, pyruvate is reduced to lactate. In the third route, pyruvate serves as a precursor for biosynthesis of three amino acids (valine, alanine, and leucine).
The second route is inefficient in terms of energy production. Specifically, conversion of one glucose molecule to lactate yields only about 5-7% of the total energy that can be set free if the glucose is oxidized completely via Krebs cycle to CO.sub.2 and H.sub.2 O.
Although it is known that pyruvate is metabolized in cutaneous tissues via at least three routes and that the conversion of pyruvate to lactate appears to be a predominant route, it is not known exactly what fraction of pyruvate is metabolized via each of the three routes. The relationship between aging and energy generation in cutaneous tissues is not entirely understood, although it has been suggested that cellular bioenergy loss accompanies aging. See e.g., Linnane, Anthony W. et al. "Mitochondrial DNA mutation and the ageing process: bioenergy and pharmacological intervention", Mutation Research, Vol. 275, (1992) pp. 195-208.
The specific lactate dehydrogenase inhibitors employed herein have been disclosed for use in topical treatment compositions. See e.g., Yu et al., U.S. Pat. No. 5,091,171. Yu et al., however, do not employ these ingredients as lactate dehydrogenase inhibitors and do not suggest their use with a specific co-active ingredient included in the present invention. Wildnauer, U.S. Pat. No. 4,294,852 discloses the use in skin treating compositions of saturated aliphatic acids having from 2-10 carbon atoms, including those acids which are substituted at either or both of the alpha and beta carbons with a hydroxyl or keto functionality, e.g., oxalic, succinic, 2-ketomalonic, 2-ketoglutaric, malic, .beta.-hydroxybutyric, glyoxylic, pyruvic, and acetoacetic acids.
Like Yu et al., Wildnauer does not employ the disclosed acids as lactate dehydrogenase inhibitors. Further, Wildnauer does not teach the specific combinations of ingredients necessary to attain the goal of the present invention, and not all acids taught by Wildnauer are suitable for use herein.
Accordingly, it is an object of the present invention to provide compositions for treatment of skin, hair, or nails.
It is another object of the invention to provide a method for treating or preventing the appearance of wrinkled, flaky, aged, photodamaged skin or skin disorders.
These and other objects of the invention will become more apparent from the detailed description and examples which follow.